Speculation arose this year regarding a significant reduction in boost pressure for the BMW M4 GT3 Evo, particularly when observing the 2026 Balance of Performance (BoP) in DTM and at the Nürburgring 24 Hours race. However, as Motorsport-Total.com discovered, the car was fitted with a new turbocharger over the winter, which accounts for the apparent difference compared to previous years. The circumstances behind this delayed FIA homologation are noteworthy.
BMW Motorsport Director Andreas Roos explained that the new turbocharger was originally slated for introduction in 2025. He stated, “But because the development time was too long – and also due to the application side of things – we eventually agreed with the FIA and the organizers to delay the introduction until 2026.”
The new turbocharger technically debuted in the M4 GT3 Evo in late November 2025 at the GT World Cup in Macau. The Bathurst 12 Hour in February 2026, however, was still run with the older turbocharger because the SRO Motorsports Group, responsible for the BoP there, conducted its traditional BoP test after that event.
Roos characterized the turbocharger change as a “cost-down measure,” elaborating, “The main reason was to drive costs down, because it is now a 1:1 series-production turbocharger, exactly as it is installed in the M3 or M4.” He added that considerations for efficiency and alternative fuels also played a role, noting that renewable components can sometimes challenge turbocharged engines. “We tried to make the application more robust in that regard,” he explained.
Regarding the car’s drivability, Roos does not anticipate any fundamental changes. He suggested there might be a “little bit” of an effect “through the application and the fact that the combustion process has been slightly adjusted.” While this could offer a “slight advantage” in one area, it might also have a “negative” impact in another, though he ultimately deems the overall change “negligible.”
Beyond the boost pressure, which is now approximately 0.3 bar lower in some instances, another notable modification with the new turbocharger is the altered Lambda value, which regulates the fuel-to-air ratio in the combustion chamber. The car now competes in the DTM with a Lambda of 0.9, a standard for other turbocharged vehicles, instead of the previous 1.1. This change means the fuel mixture is less lean, making the BMW less fuel-efficient than it previously was.
Addressing paddock rumors that linked the change to allegations from competitors about the BMW potentially accessing unexpected additional power, Roos firmly denied any connection. “No, that is not true – it has absolutely nothing to do with that,” Roos clarified. “It was our approach, together with the FIA, to change this.”
Despite Roos’s denial, and the absence of a direct link to the allegations made by Manthey last year at the Nürburgring 24 Hours race and the DTM finale at Hockenheim, the alteration to the turbocharger was reportedly not entirely voluntary.
Motorsport-Total.com learned from multiple independent sources that the FIA had reportedly mandated a change to the previous turbocharger. This was reportedly due to the fact that it did not meet the regulatory and homologation requirement of being a 1:1 series-production model.
While the exterior of the previous charger was said to be identical, its internal components were reportedly not 100 percent congruent with the road-going version. The replacement was initially scheduled for last year’s racing season but was deferred until the season’s conclusion, partly because of its significant potential impact on the Balance of Performance, given the turbocharger’s fundamental role in the vehicle.
On the question of whether this irregularity was intentional, Motorsport-Total.com’s understanding suggests it is entirely plausible that a misunderstanding occurred during the car’s initial homologation, leading the FIA, despite its earlier inspection, to only become aware of the issue in 2025.
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